Hunters often try to track wounded game by following a blood trail. Law enforcement officers and military personnel may also need to track a trail of blood. Following a blood trail at night may be challenging because blood is often difficult to identify at night, even if the tracker is using a high-powered flashlight. One problem with traditional flashlights is that they may flood a user's eye with a broad spectrum of light, making it difficult for the user to distinguish between the color(s) of blood and other colors.
Traditional light sources have limited effectiveness as they are not optimized to the optical properties of blood or to the response of the human vision system. Traditional light sources used today to locate blood utilize a variety of elements such as bulbs (incandescent, xenon, or halogen), light emitting diodes (white LEDs), and burning gases (lanterns). These lights are not optimized to the reflective properties of blood or to the visual response of the human eye. Incandescent bulbs produce a yellow cast (yellowish/white). Many of the white LEDs available today have a blue cast (bluish/white). Many high intensity white light sources tend to saturate the human eye.
Application specific light sources may be optimized to the optical properties of blood and to the related response of the human vision system. However, these devices use combinations of colored light sources (e.g., additive methods) that produce colored interference shadows, which may create significant distraction when tracking blood in brush and tall grass. Application specific lights utilize an additive method whereby combinations of lighting elements (e.g., green and red LEDs, or blue and red LEDS). While these combinations produce output spectrums that enhance the detection of blood, they may have the drawback of producing colored interference shadows. In an outdoor environment, colored shadows appear on the ground when tracking blood in tall grass or brush. These devices cast the obvious dark shadows on the ground when shining through the brush. These shadows are also outlined with thin colored boarders (e.g., green and red, or blue and red), which may be distractions to the user.